A 19F-NMR study of the equilibrium unfolding of membrane-associated D-lactate dehydro
 

A 19F-NMR study of the equilibrium unfolding of membrane-associated D-lactate dehydrogenase of Escherichia coli.

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Biochemistry. 1996 Dec 24;35(51):16502-9

Authors: Sun ZY, Pratt EA, Simplaceanu V, Ho C

Partially folded protein intermediates have been observed by 19F-NMR spectroscopy during the equilibrium unfolding of the membrane-associated D-lactate dehydrogenase (D-LDH) of Escherichia coli by a denaturant, guanidine hydrochloride (Gdn.HCl). The results from 19F-NMR and circular dichroism spectroscopic studies suggest that the intermediates observed at low Gdn.HCl concentrations (< 3.5 M) exhibit features similar to "molten globules" that contain considerable amounts of secondary and tertiary structure. The results of 19F-NMR studies on 5F-Trp-labeled D-LDH, such as the chemical shift changes, nuclear Overhauser effect, and solvent-induced isotopic shift effect, show that different regions of D-LDH unfold nonuniformly in Gdn.HCl in the presence of lysophosphatidylcholine. The polypeptide appears to unfold in a general order from the carboxyl end to the amino end, in agreement with previous findings from our laboratory that the carboxyl-terminal region of D-LDH is largely exposed to the solvent while the amino-terminal region is buried in the protein core. The structure of the partially unfolded intermediate forms of D-LDH is stabilized in the presence of lipid-like detergents, such as lysophosphatidylcholine.

PMID: 8987983 [PubMed - indexed for MEDLINE]



Source: PubMed